Repair of PenF lens 42/1.2 with fogging

[Sonnar2]

Hi folks,

The repair of the foggy 42/1.2 PenF lens was on my list (usable but with very low contrast). Last weekend I unscrewed it from front, and the 2nd and 3rd element (a cemented doublet) came out nicely.
The fog is right between the elements. So next step would be to segregate them, clean, and re-cement them with canada balsam. But I find no way to lose the ring holding the doublet. No threads whatsoever. Could it be pressed together? Don't want to apply any force here.
Anyone has repaired this lens already? I have seen some 42/1.2 lenses offered with fungus/fogging, so this is a common fault probably.
I already asked a repair guy who works with Olympus here in Germany but with no effect.

It would be a shame to leave it uncured because it's a very nice example of that quite rare lens.

Any help would be appreciated.
Cheers, S.

 

[Sarcophilus Harrisii]

How were you planning to separate the glass components?

 

[Sonnar2]

I would try JonGodman's method.

 

[Landshark]

More than one lens is assembled this way & they're kind of a pain to get apart.

Looking at the second picture, there's a ring at the bottom of the straight section of glass. On the right side, it looks like someone tried this & stopped.
I remove the paint with Acetone and using a small ~1mm screwdriver or #11 blade in an X-Acto knife, work around the edge applying enough pressure to barely pry the metal edge away from the glass. This IS going to take a while. Prying too hard will break the metal(done it) or damage the glass.
In at least one lens after spreading the retainer I wasn't able to remove the anyway, so reassembled & lived with it.

I've never used Jon's method using a light bulb. I'm gonna try that next time and have tried the boiling water method with no success. Found that using paint stripper has been very good. That's Methylene(?)/Methyl(?) Chloride. Anyway, paint stripper.

 

[Erik van Straten]

I've heard from an official Olympus-repairer that he puts the cemented lenses above a flame so that the Canada-balsam melts and becomes clear. There is the danger that one of the lenses - or both - will crack.

Erik.

 

[Sonnar2]

Update:
I applied moderate heat (placing the lensgroup over an old-fashioned 100W lightbulb for 30m, not exceeding 100°C) and it turned loose. Surprise: The second element hold just with adhesion power, no screwing nor flanging. The black edge isn't metal, just painted glass. (of course the edge needs to be painted to extinct stray light)
Before it went loose, the balsam between the elements started melting, fogging decreased, but not fully disappeared, so I decided to separate the elements. Cleaning them with dilution agent, a small area in the bigger, covered lens remained with slight haze: maybe glass damaged by fungus, maybe relicts of hardened balsam that couldn't washed out. But even this way it looks 95% better than before.
Intermediate result: Olympus kept using old-fashioned agents like canada balsam for glueing optical elements in the 1960's. This is good news for restoring them, because they can be dissolved without restraint, which is not so sure for newer, high-tech gluing stuff.

So I stored them back, ordering Flitz polish, for cleaning the glass (need to buy it in US because no non-abrasive polish agents found on the European market) and canada balsam (the type of microscopic/optical usage) for re-gluing them.

cheers,

 

[Sarcophilus Harrisii]

I was going to suggest sourcing some Milsolve to separate the glass but it seems you've got there anyway without it.
Cheers
Brett

 

[Sonnar2]

2nd Update:

After polishing with non-abrasive agents and reglueing with canada balsam I stored it away for 3 months. I gave some extra time because just the glue hold the element together, no retaining ring present. At the end finishing the edges with black paint, just like it was before. Re-Mounting is easy.

Result: the lens is clear like a bell and works again.